From 3f03940fcb23602353180ca5d7ec8cbece537c7d Mon Sep 17 00:00:00 2001
From: MS <disinvite@users.noreply.github.com>
Date: Sat, 23 Mar 2024 18:01:40 -0400
Subject: [PATCH] Match vtables with virtual inheritance (#717)

* Match vtables with virtual inheritance

* Simplify vtable name check

* Thunk alert
---
 tools/isledecomp/isledecomp/compare/core.py   | 100 +++++++++++++++++-
 tools/isledecomp/isledecomp/compare/db.py     |  64 ++++++++++-
 .../isledecomp/isledecomp/cvdump/demangler.py |  51 ++++++++-
 tools/isledecomp/isledecomp/parser/marker.py  |  21 +++-
 tools/isledecomp/isledecomp/parser/node.py    |   2 +-
 tools/isledecomp/isledecomp/parser/parser.py  |  12 ++-
 tools/isledecomp/tests/test_demangler.py      |  33 +++++-
 tools/isledecomp/tests/test_parser.py         |  43 ++++++++
 tools/isledecomp/tests/test_parser_util.py    |  32 ++++++
 tools/requirements.txt                        |   1 +
 tools/vtable/vtable.py                        |  15 +++
 11 files changed, 350 insertions(+), 24 deletions(-)

diff --git a/tools/isledecomp/isledecomp/compare/core.py b/tools/isledecomp/isledecomp/compare/core.py
index 3d2246e4..ec49f70b 100644
--- a/tools/isledecomp/isledecomp/compare/core.py
+++ b/tools/isledecomp/isledecomp/compare/core.py
@@ -86,6 +86,7 @@ def __init__(
         self._find_original_strings()
         self._match_thunks()
         self._match_exports()
+        self._find_vtordisp()
 
     def _load_cvdump(self):
         logger.info("Parsing %s ...", self.pdb_file)
@@ -198,7 +199,7 @@ def _load_markers(self):
                 self._db.match_variable(var.offset, var.name)
 
         for tbl in codebase.iter_vtables():
-            self._db.match_vtable(tbl.offset, tbl.name)
+            self._db.match_vtable(tbl.offset, tbl.name, tbl.base_class)
 
         for string in codebase.iter_strings():
             # Not that we don't trust you, but we're checking the string
@@ -285,10 +286,105 @@ def _match_exports(self):
             ):
                 logger.debug("Matched export %s", repr(export_name))
 
+    def _find_vtordisp(self):
+        """If there are any cases of virtual inheritance, we can read
+        through the vtables for those classes and find the vtable thunk
+        functions (vtordisp).
+
+        Our approach is this: walk both vtables and check where we have a
+        vtordisp in the recomp table. Inspect the function at that vtable
+        position (in both) and check whether we jump to the same function.
+
+        One potential pitfall here is that the virtual displacement could
+        differ between the thunks. We are not (yet) checking for this, so the
+        result is that the vtable will appear to match but we will have a diff
+        on the thunk in our regular function comparison.
+
+        We could do this differently and check only the original vtable,
+        construct the name of the vtordisp function and match based on that."""
+
+        for match in self._db.get_matches_by_type(SymbolType.VTABLE):
+            # We need some method of identifying vtables that
+            # might have thunks, and this ought to work okay.
+            if "{for" not in match.name:
+                continue
+
+            # TODO: We might want to fix this at the source (cvdump) instead.
+            # Any problem will be logged later when we compare the vtable.
+            vtable_size = 4 * (match.size // 4)
+            orig_table = self.orig_bin.read(match.orig_addr, vtable_size)
+            recomp_table = self.recomp_bin.read(match.recomp_addr, vtable_size)
+
+            raw_addrs = zip(
+                [t for (t,) in struct.iter_unpack("<L", orig_table)],
+                [t for (t,) in struct.iter_unpack("<L", recomp_table)],
+            )
+
+            # Now walk both vtables looking for thunks.
+            for orig_addr, recomp_addr in raw_addrs:
+                if not self._db.is_vtordisp(recomp_addr):
+                    continue
+
+                thunk_fn = self.get_by_recomp(recomp_addr)
+
+                # Read the function bytes here.
+                # In practice, the adjuster thunk will be under 16 bytes.
+                # If we have thunks of unequal size, we can still tell whether
+                # they are thunking the same function by grabbing the
+                # JMP instruction at the end.
+                thunk_presumed_size = max(thunk_fn.size, 16)
+
+                # Strip off MSVC padding 0xcc bytes.
+                # This should be safe to do; it is highly unlikely that
+                # the MSB of the jump displacement would be 0xcc. (huge jump)
+                orig_thunk_bin = self.orig_bin.read(
+                    orig_addr, thunk_presumed_size
+                ).rstrip(b"\xcc")
+
+                recomp_thunk_bin = self.recomp_bin.read(
+                    recomp_addr, thunk_presumed_size
+                ).rstrip(b"\xcc")
+
+                # Read jump opcode and displacement (last 5 bytes)
+                (orig_jmp, orig_disp) = struct.unpack("<Bi", orig_thunk_bin[-5:])
+                (recomp_jmp, recomp_disp) = struct.unpack("<Bi", recomp_thunk_bin[-5:])
+
+                # Make sure it's a JMP
+                if orig_jmp != 0xE9 or recomp_jmp != 0xE9:
+                    continue
+
+                # Calculate jump destination from the end of the JMP instruction
+                # i.e. the end of the function
+                orig_actual = orig_addr + len(orig_thunk_bin) + orig_disp
+                recomp_actual = recomp_addr + len(recomp_thunk_bin) + recomp_disp
+
+                # If they are thunking the same function, then this must be a match.
+                if self.is_pointer_match(orig_actual, recomp_actual):
+                    if len(orig_thunk_bin) != len(recomp_thunk_bin):
+                        logger.warning(
+                            "Adjuster thunk %s (0x%x) is not exact",
+                            thunk_fn.name,
+                            orig_addr,
+                        )
+                    self._db.set_function_pair(orig_addr, recomp_addr)
+
     def _compare_function(self, match: MatchInfo) -> DiffReport:
         orig_raw = self.orig_bin.read(match.orig_addr, match.size)
         recomp_raw = self.recomp_bin.read(match.recomp_addr, match.size)
 
+        # It's unlikely that a function other than an adjuster thunk would
+        # start with a SUB instruction, so alert to a possible wrong
+        # annotation here.
+        # There's probably a better place to do this, but we're reading
+        # the function bytes here already.
+        try:
+            if orig_raw[0] == 0x2B and recomp_raw[0] != 0x2B:
+                logger.warning(
+                    "Possible thunk at 0x%x (%s)", match.orig_addr, match.name
+                )
+        except IndexError:
+            pass
+
         def orig_lookup(addr: int) -> Optional[str]:
             m = self._db.get_by_orig(addr)
             if m is None:
@@ -432,7 +528,7 @@ def match_text(m: Optional[MatchInfo], raw_addr: Optional[int] = None) -> str:
             match_type=SymbolType.VTABLE,
             orig_addr=match.orig_addr,
             recomp_addr=match.recomp_addr,
-            name=f"{match.name}::`vftable'",
+            name=match.name,
             udiff=unified_diff,
             ratio=ratio,
         )
diff --git a/tools/isledecomp/isledecomp/compare/db.py b/tools/isledecomp/isledecomp/compare/db.py
index 54ae8081..f758be0c 100644
--- a/tools/isledecomp/isledecomp/compare/db.py
+++ b/tools/isledecomp/isledecomp/compare/db.py
@@ -4,6 +4,7 @@
 import logging
 from typing import List, Optional
 from isledecomp.types import SymbolType
+from isledecomp.cvdump.demangler import get_vtordisp_name
 
 _SETUP_SQL = """
     DROP TABLE IF EXISTS `symbols`;
@@ -249,6 +250,37 @@ def get_match_options(self, addr: int) -> Optional[dict]:
             for (option, value) in cur.fetchall()
         }
 
+    def is_vtordisp(self, recomp_addr: int) -> bool:
+        """Check whether this function is a vtordisp based on its
+        decorated name. If its demangled name is missing the vtordisp
+        indicator, correct that."""
+        row = self._db.execute(
+            """SELECT name, decorated_name
+            FROM `symbols`
+            WHERE recomp_addr = ?""",
+            (recomp_addr,),
+        ).fetchone()
+
+        if row is None:
+            return False
+
+        (name, decorated_name) = row
+        if "`vtordisp" in name:
+            return True
+
+        new_name = get_vtordisp_name(decorated_name)
+        if new_name is None:
+            return False
+
+        self._db.execute(
+            """UPDATE `symbols`
+            SET name = ?
+            WHERE recomp_addr = ?""",
+            (new_name, recomp_addr),
+        )
+
+        return True
+
     def _find_potential_match(
         self, name: str, compare_type: SymbolType
     ) -> Optional[int]:
@@ -323,12 +355,34 @@ def match_function(self, addr: int, name: str) -> bool:
 
         return did_match
 
-    def match_vtable(self, addr: int, name: str) -> bool:
-        did_match = self._match_on(SymbolType.VTABLE, addr, name)
-        if not did_match:
-            logger.error("Failed to find vtable for class: %s", name)
+    def match_vtable(
+        self, addr: int, name: str, base_class: Optional[str] = None
+    ) -> bool:
+        # Only allow a match against "Class:`vftable'"
+        # if this is the derived class.
+        name = (
+            f"{name}::`vftable'"
+            if base_class is None or base_class == name
+            else f"{name}::`vftable'{{for `{base_class}'}}"
+        )
 
-        return did_match
+        row = self._db.execute(
+            """
+            SELECT recomp_addr
+            FROM `symbols`
+            WHERE orig_addr IS NULL
+            AND name = ?
+            AND (compare_type = ?)
+            LIMIT 1
+            """,
+            (name, SymbolType.VTABLE.value),
+        ).fetchone()
+
+        if row is not None and self.set_pair(addr, row[0], SymbolType.VTABLE):
+            return True
+
+        logger.error("Failed to find vtable for class: %s", name)
+        return False
 
     def match_static_variable(self, addr: int, name: str, function_addr: int) -> bool:
         """Matching a static function variable by combining the variable name
diff --git a/tools/isledecomp/isledecomp/cvdump/demangler.py b/tools/isledecomp/isledecomp/cvdump/demangler.py
index 10984bff..9b2445da 100644
--- a/tools/isledecomp/isledecomp/cvdump/demangler.py
+++ b/tools/isledecomp/isledecomp/cvdump/demangler.py
@@ -5,6 +5,7 @@
 import re
 from collections import namedtuple
 from typing import Optional
+import pydemangler
 
 
 class InvalidEncodedNumberError(Exception):
@@ -51,8 +52,52 @@ def demangle_string_const(symbol: str) -> Optional[StringConstInfo]:
     return StringConstInfo(len=strlen, is_utf16=is_utf16)
 
 
+def get_vtordisp_name(symbol: str) -> Optional[str]:
+    # pylint: disable=c-extension-no-member
+    """For adjuster thunk functions, the PDB will sometimes use a name
+    that contains "vtordisp" but often will just reuse the name of the
+    function being thunked. We want to use the vtordisp name if possible."""
+    name = pydemangler.demangle(symbol)
+    if name is None:
+        return None
+
+    if "`vtordisp" not in name:
+        return None
+
+    # Now we remove the parts of the friendly name that we don't need
+    try:
+        # Assuming this is the last of the function prefixes
+        thiscall_idx = name.index("__thiscall")
+        # To match the end of the `vtordisp{x,y}' string
+        end_idx = name.index("}'")
+        return name[thiscall_idx + 11 : end_idx + 2]
+    except ValueError:
+        return name
+
+
 def demangle_vtable(symbol: str) -> str:
+    # pylint: disable=c-extension-no-member
     """Get the class name referenced in the vtable symbol."""
+    raw = pydemangler.demangle(symbol)
+
+    if raw is None:
+        pass  # TODO: This shouldn't happen if MSVC behaves
+
+    # Remove storage class and other stuff we don't care about
+    return (
+        raw.replace("<class ", "<")
+        .replace("<struct ", "<")
+        .replace("const ", "")
+        .replace("volatile ", "")
+    )
+
+
+def demangle_vtable_ourselves(symbol: str) -> str:
+    """Parked implementation of MSVC symbol demangling.
+    We only use this for vtables and it works okay with the simple cases or
+    templates that refer to other classes/structs. Some namespace support.
+    Does not support backrefs, primitive types, or vtables with
+    virtual inheritance."""
 
     # Seek ahead 4 chars to strip off "??_7" prefix
     t = symbol[4:].split("@")
@@ -66,11 +111,11 @@ def demangle_vtable(symbol: str) -> str:
         else:
             generic = t[1][1:]
 
-        return f"{class_name}<{generic}>"
+        return f"{class_name}<{generic}>::`vftable'"
 
     # If we have two classes listed, it is a namespace hierarchy.
     # @@6B@ is a common generic suffix for these vtable symbols.
     if t[1] != "" and t[1] != "6B":
-        return t[1] + "::" + t[0]
+        return t[1] + "::" + t[0] + "::`vftable'"
 
-    return t[0]
+    return t[0] + "::`vftable'"
diff --git a/tools/isledecomp/isledecomp/parser/marker.py b/tools/isledecomp/isledecomp/parser/marker.py
index de8c6f05..8108ac46 100644
--- a/tools/isledecomp/isledecomp/parser/marker.py
+++ b/tools/isledecomp/isledecomp/parser/marker.py
@@ -1,5 +1,5 @@
 import re
-from typing import Optional
+from typing import Optional, Tuple
 from enum import Enum
 
 
@@ -29,18 +29,20 @@ class MarkerType(Enum):
 
 
 markerRegex = re.compile(
-    r"\s*//\s*(?P<type>\w+):\s*(?P<module>\w+)\s+(?P<offset>0x[a-f0-9]+)",
+    r"\s*//\s*(?P<type>\w+):\s*(?P<module>\w+)\s+(?P<offset>0x[a-f0-9]+) *(?P<extra>\S.+\S)?",
     flags=re.I,
 )
 
 
 markerExactRegex = re.compile(
-    r"\s*// (?P<type>[A-Z]+): (?P<module>[A-Z0-9]+) (?P<offset>0x[a-f0-9]+)$"
+    r"\s*// (?P<type>[A-Z]+): (?P<module>[A-Z0-9]+) (?P<offset>0x[a-f0-9]+)(?: (?P<extra>\S.+\S))?\n?$"
 )
 
 
 class DecompMarker:
-    def __init__(self, marker_type: str, module: str, offset: int) -> None:
+    def __init__(
+        self, marker_type: str, module: str, offset: int, extra: Optional[str] = None
+    ) -> None:
         try:
             self._type = MarkerType[marker_type.upper()]
         except KeyError:
@@ -51,6 +53,7 @@ def __init__(self, marker_type: str, module: str, offset: int) -> None:
         # we will emit a syntax error.
         self._module: str = module.upper()
         self._offset: int = offset
+        self._extra: Optional[str] = extra
 
     @property
     def type(self) -> MarkerType:
@@ -64,6 +67,10 @@ def module(self) -> str:
     def offset(self) -> int:
         return self._offset
 
+    @property
+    def extra(self) -> Optional[str]:
+        return self._extra
+
     @property
     def category(self) -> MarkerCategory:
         if self.is_vtable():
@@ -81,6 +88,11 @@ def category(self) -> MarkerCategory:
 
         return MarkerCategory.ADDRESS
 
+    @property
+    def key(self) -> Tuple[str, str, Optional[str]]:
+        """For use with the MarkerDict. To detect/avoid marker collision."""
+        return (self.category, self.module, self.extra)
+
     def is_regular_function(self) -> bool:
         """Regular function, meaning: not an explicit byname lookup. FUNCTION
         markers can be _implicit_ byname.
@@ -126,6 +138,7 @@ def match_marker(line: str) -> Optional[DecompMarker]:
         marker_type=match.group("type"),
         module=match.group("module"),
         offset=int(match.group("offset"), 16),
+        extra=match.group("extra"),
     )
 
 
diff --git a/tools/isledecomp/isledecomp/parser/node.py b/tools/isledecomp/isledecomp/parser/node.py
index eeaed713..21e4c382 100644
--- a/tools/isledecomp/isledecomp/parser/node.py
+++ b/tools/isledecomp/isledecomp/parser/node.py
@@ -55,7 +55,7 @@ class ParserVariable(ParserSymbol):
 
 @dataclass
 class ParserVtable(ParserSymbol):
-    pass
+    base_class: Optional[str] = None
 
 
 @dataclass
diff --git a/tools/isledecomp/isledecomp/parser/parser.py b/tools/isledecomp/isledecomp/parser/parser.py
index 2e5daf07..b2534548 100644
--- a/tools/isledecomp/isledecomp/parser/parser.py
+++ b/tools/isledecomp/isledecomp/parser/parser.py
@@ -47,15 +47,16 @@ def __init__(self) -> None:
 
     def insert(self, marker: DecompMarker) -> bool:
         """Return True if this insert would overwrite"""
-        key = (marker.category, marker.module)
-        if key in self.markers:
+        if marker.key in self.markers:
             return True
 
-        self.markers[key] = marker
+        self.markers[marker.key] = marker
         return False
 
-    def query(self, category: MarkerCategory, module: str) -> Optional[DecompMarker]:
-        return self.markers.get((category, module))
+    def query(
+        self, category: MarkerCategory, module: str, extra: Optional[str] = None
+    ) -> Optional[DecompMarker]:
+        return self.markers.get((category, module, extra))
 
     def iter(self) -> Iterator[DecompMarker]:
         for _, marker in self.markers.items():
@@ -275,6 +276,7 @@ def _vtable_done(self, class_name: str = None):
                     module=marker.module,
                     offset=marker.offset,
                     name=self.curly.get_prefix(class_name),
+                    base_class=marker.extra,
                 )
             )
 
diff --git a/tools/isledecomp/tests/test_demangler.py b/tools/isledecomp/tests/test_demangler.py
index e40d6e0c..f7c806e1 100644
--- a/tools/isledecomp/tests/test_demangler.py
+++ b/tools/isledecomp/tests/test_demangler.py
@@ -4,6 +4,7 @@
     demangle_vtable,
     parse_encoded_number,
     InvalidEncodedNumberError,
+    get_vtordisp_name,
 )
 
 string_demangle_cases = [
@@ -46,13 +47,37 @@ def test_invalid_encoded_number():
 
 
 vtable_cases = [
-    ("??_7LegoCarBuildAnimPresenter@@6B@", "LegoCarBuildAnimPresenter"),
-    ("??_7?$MxCollection@PAVLegoWorld@@@@6B@", "MxCollection<LegoWorld *>"),
-    ("??_7?$MxPtrList@VLegoPathController@@@@6B@", "MxPtrList<LegoPathController>"),
-    ("??_7Renderer@Tgl@@6B@", "Tgl::Renderer"),
+    ("??_7LegoCarBuildAnimPresenter@@6B@", "LegoCarBuildAnimPresenter::`vftable'"),
+    ("??_7?$MxCollection@PAVLegoWorld@@@@6B@", "MxCollection<LegoWorld *>::`vftable'"),
+    (
+        "??_7?$MxPtrList@VLegoPathController@@@@6B@",
+        "MxPtrList<LegoPathController>::`vftable'",
+    ),
+    ("??_7Renderer@Tgl@@6B@", "Tgl::Renderer::`vftable'"),
+    ("??_7LegoExtraActor@@6B0@@", "LegoExtraActor::`vftable'{for `LegoExtraActor'}"),
+    (
+        "??_7LegoExtraActor@@6BLegoAnimActor@@@",
+        "LegoExtraActor::`vftable'{for `LegoAnimActor'}",
+    ),
+    (
+        "??_7LegoAnimActor@@6B?$LegoContainer@PAM@@@",
+        "LegoAnimActor::`vftable'{for `LegoContainer<float *>'}",
+    ),
 ]
 
 
 @pytest.mark.parametrize("symbol, class_name", vtable_cases)
 def test_vtable(symbol, class_name):
     assert demangle_vtable(symbol) == class_name
+
+
+def test_vtordisp():
+    """Make sure we can accurately detect an adjuster thunk symbol"""
+    assert get_vtordisp_name("") is None
+    assert get_vtordisp_name("?ClassName@LegoExtraActor@@UBEPBDXZ") is None
+    assert (
+        get_vtordisp_name("?ClassName@LegoExtraActor@@$4PPPPPPPM@A@BEPBDXZ") is not None
+    )
+
+    # A function called vtordisp
+    assert get_vtordisp_name("?vtordisp@LegoExtraActor@@UBEPBDXZ") is None
diff --git a/tools/isledecomp/tests/test_parser.py b/tools/isledecomp/tests/test_parser.py
index 772a39c4..bbc3b739 100644
--- a/tools/isledecomp/tests/test_parser.py
+++ b/tools/isledecomp/tests/test_parser.py
@@ -711,3 +711,46 @@ def test_header_function_declaration(parser):
 
     assert len(parser.alerts) == 1
     assert parser.alerts[0].code == ParserError.NO_IMPLEMENTATION
+
+
+def test_extra(parser):
+    """Allow a fourth field in the decomp annotation. Its use will vary
+    depending on the marker type. Currently this is only used to identify
+    a vtable with virtual inheritance."""
+
+    # Intentionally using non-vtable markers here.
+    # We might want to emit a parser warning for unnecessary extra info.
+    parser.read_lines(
+        [
+            "// GLOBAL: TEST 0x5555 Haha",
+            "int g_variable = 0;",
+            "// FUNCTION: TEST 0x1234 Something",
+            "void Test() { g_variable++; }",
+            "// LIBRARY: TEST 0x8080 Printf",
+            "// _printf",
+        ]
+    )
+
+    # We don't use this information (yet) but this is all fine.
+    assert len(parser.alerts) == 0
+
+
+def test_virtual_inheritance(parser):
+    """Indicate the base class for a vtable where the class uses
+    virtual inheritance."""
+    parser.read_lines(
+        [
+            "// VTABLE: HELLO 0x1234",
+            "// VTABLE: HELLO 0x1238 Greetings",
+            "// VTABLE: HELLO 0x123c Howdy",
+            "class HiThere : public virtual Greetings {",
+            "};",
+        ]
+    )
+
+    assert len(parser.alerts) == 0
+    assert len(parser.vtables) == 3
+    assert parser.vtables[0].base_class is None
+    assert parser.vtables[1].base_class == "Greetings"
+    assert parser.vtables[2].base_class == "Howdy"
+    assert all(v.name == "HiThere" for v in parser.vtables)
diff --git a/tools/isledecomp/tests/test_parser_util.py b/tools/isledecomp/tests/test_parser_util.py
index 8a403710..9936c5bc 100644
--- a/tools/isledecomp/tests/test_parser_util.py
+++ b/tools/isledecomp/tests/test_parser_util.py
@@ -65,6 +65,14 @@ def test_is_blank_or_comment(line: str, expected: bool):
     # TODO: These match but shouldn't.
     # (False, False, '// FUNCTION: LEGO1 0'),
     # (False, False, '// FUNCTION: LEGO1 0x'),
+    # Extra field
+    (True, True, "// VTABLE: HELLO 0x1234 Extra"),
+    # Extra with spaces
+    (True, True, "// VTABLE: HELLO 0x1234 Whatever<SubClass *>"),
+    # Extra, no space (if the first non-hex character is not in [a-f])
+    (True, False, "// VTABLE: HELLO 0x1234Hello"),
+    # Extra, many spaces
+    (True, False, "// VTABLE: HELLO 0x1234    Hello"),
 ]
 
 
@@ -174,3 +182,27 @@ def test_get_variable_name(line: str, name: str):
 @pytest.mark.parametrize("line, string", string_match_cases)
 def test_get_string_contents(line: str, string: str):
     assert get_string_contents(line) == string
+
+
+def test_marker_extra_spaces():
+    """The extra field can contain spaces"""
+    marker = match_marker("// VTABLE: TEST 0x1234 S p a c e s")
+    assert marker.extra == "S p a c e s"
+
+    # Trailing spaces removed
+    marker = match_marker("// VTABLE: TEST 0x8888 spaces    ")
+    assert marker.extra == "spaces"
+
+    # Trailing newline removed if present
+    marker = match_marker("// VTABLE: TEST 0x5555 newline\n")
+    assert marker.extra == "newline"
+
+
+def test_marker_trailing_spaces():
+    """Should ignore trailing spaces. (Invalid extra field)
+    Offset field not truncated, extra field set to None."""
+
+    marker = match_marker("// VTABLE: TEST 0x1234     ")
+    assert marker is not None
+    assert marker.offset == 0x1234
+    assert marker.extra is None
diff --git a/tools/requirements.txt b/tools/requirements.txt
index 5875ae35..b23ca4fb 100644
--- a/tools/requirements.txt
+++ b/tools/requirements.txt
@@ -5,3 +5,4 @@ colorama
 isledecomp
 pystache
 pyyaml
+git+https://github.com/wbenny/pydemangler.git
diff --git a/tools/vtable/vtable.py b/tools/vtable/vtable.py
index eb09412c..c5dc27a7 100755
--- a/tools/vtable/vtable.py
+++ b/tools/vtable/vtable.py
@@ -89,6 +89,21 @@ def main():
 
         print_summary(vtable_count, problem_count)
 
+        # Now compare adjuster thunk functions, if there are any.
+        # These matches are generated by the compare engine.
+        # They should always match 100%. If not, there is a problem
+        # with the inheritance or an overriden function.
+        for fun_match in engine.get_functions():
+            if "`vtordisp" not in fun_match.name:
+                continue
+
+            diff = engine.compare_address(fun_match.orig_addr)
+            if diff.ratio < 1.0:
+                problem_count += 1
+                print(
+                    f"Problem with adjuster thunk {fun_match.name} (0x{fun_match.orig_addr:x} / 0x{fun_match.recomp_addr:x})"
+                )
+
     return 1 if problem_count > 0 else 0